The present invention relates to an improved process for preparing legumes exhibiting reduced flatulence when digested by mammals and a process for reducing flatulence in legumes when digested by mammals and the products thus prepared.
Legumes are important foodstuffs and are likely to become more so in the future. For example, many legumes, especially those in some of the legume genuses, such as Phaseolus, Soja and Lens, are high in protein and provide an inexpensive alternative to animal protein.
Unfortunately, ingestion of some of the most nutritious and abundant legumes can be accompanied by severe flatulence as well as abdominal distress and poor digestibility. More specifically, the flatulence results in discomfort, diarrhea, loss of appetite, and poor growth, all of which have prevented the wide-scale use of these vegetable nutrients.
It is believed that the flatulence is due to various factors. For example, it has been postulated that the flatulence is attributable to the indigestibility by mammalian digestive enzymes of the flatulence-causing alpha oligosaccharides, such as raffinose, stachyose, and verbascose, and the like, present in legume products. The generally accepted explanation of the action of the alpha oligosaccharides in producing flatulence is that the enzyme alpha galactosidase, which hydrolyzes the xcex1-oligosaccharides, is not present in the intestinal tract of mammals. Thus, these compounds are not hydrolyzed and dissolved in the digestive tract so that they can be absorbed. Instead, they reach the lower intestine essentially intact. Here, anaerobic bacteria ferment these sugars with the resultant production of carbon dioxide, hydrogen, and methane gases, thereby producing flatus.
However, these xcex1-oligosaccharides are believed not to be the only source present in the legume that causes flatulence. It has been reported that flatulence is also due to components present in the cell wall fiber constituents. Other have conjectured that undigested starch and protein in the legumes are contributing factors to flatus production.
Various solutions have been proposed to reduce flatulence in legumes, but many of these focus on just one of the factors described hereinabove, viz., the flatulence-causing oligosaccharides. More specifically, many proposed solutions relate to the use of enzymes to enhance the digestibility of the oligosaccharides. Thus, one solution is to add oligosaccharide-digesting enzymes to the legume itself or as a food supplement to be ingested substantially simultaneously with the ingestion of the legume. For example, U.S. Pat. No. 3,632,646 to Sherba discloses the addition to foodstuff, such as legumes, of xcex1-galactosidases or other enzyme preparations capable of hydrolyzing the 1,6-linkages of stachyose and other food containing flatulence-causing polysaccharides. U.S. Pat. Nos. 4,376,127 and 4,376,128 to Lunde disclose a process of improving the digestibility of legumes and reducing the flatulence thereof by adding an enzyme system found in pineapple and papaya to the legumes prior to cooking said legumes. U.S. Pat. No. 5,651,967 to Rohde, Jr., et al. discloses a food supplement comprising a beta-fructofuranosidase which is alleged to enhance the digestibility of sugars and reduce flatulence. U.S. Pat. Nos. 5,445,957 and 5,651,967 disclose a food supplement to be ingested simultaneously with the legume comprising a beta-fructofurnanosidase enzyme, a cellulose enzyme and a hemicellulose enzyme which together alleviate gastrointestinal distress caused from the digestion of legumes.
Another solution is leaching the oligosaccharides from the legumes. For example, one method is to soak the legume product in water. Sometimes, the soak is in hot water that gradually cools as the soaking progresses. The soaking water may or may not be changed with fresh water. By this method, it has been found that soaking significantly decreases the xcex1-galactoside content in lentils. (See, Frias, et al, Journal of Food Protection, 1995, 58, 692-695.) In addition, it has been found that cooking, by either boiling or pressure cooking, also decreases the xcex1-galactoside content. (See, Vidal-Valverde, et al., Journal of American Dietetic Association, 1993, 93, 547-550).
Industrial soaking, which can be used to leach the oligosaccharides from the legumes, falls into two main processes. The most practiced is an ambient or initially warm soak that is allowed to cool naturally for several hours, followed by a very short blanch at typically 180xc2x0 F. The high controlled-temperature blanch is used to optimize initial rehydration, deaerate the legumes and coagulate the protein to prevent starch leaching out of the legumes during cooking.
A second industrial process is to use multiple short soak times at temperatures sufficient to accelerate the rehydration process. In this process, the legumes are heated in a series of blanchers.
Other methods utilized and/or proposed to reduce flatulence include dehulling of the bean (See U.S. Pat. No. 202,975); fermenting the legume with a microbe (See, Goel, et al., Indian J. Nutr. Dictet, 1980, 18, 215-217); and germinating the legume (See, e.g., Rao, et al. J. Agric Food Chem., 1978, 26, 316-319). In fact, Rao, et al. in the Journal of Food Science, 1983, 1791-1795, disclose that xcex3-irradiation is effective for elimination of flatulence-causing oligosaccharides in legumes during germination.
In the Ph.D. thesis of Matrid King from the University of Arkansas (1987), the use of endogenous xcex1-galactosidase in cowpeas was explored for the purpose of removing the flatulence-causing oligosaccharides therefrom. For example, soaking, germination, and fermentative and non-fermentative incubation treatments for stimulating xcex1galactosidase hydrolysis of the oligosaccharides were investigated. The thesis disclosed that the enzyme activity of the xcex1-galactosidase increased until a temperature maximum of 113xc2x0 F. was obtained, i.e., above this temperature the enzyme activity decreased. For example, a two minute incubation at 50xc2x0 C. (122xc2x0 F.), 55xc2x0 C. (129xc2x0 F.) and 60xc2x0 C. (140xc2x0 F.) resulted in a 50, 70 and 90% loss of activity compared to the activity at 113xc2x0 F. In addition, King disclosed that endogenous xcex1galactosidase has maximum enzymatic activity at a pH ranging between 4.0 and 5.0.
Although these methods described hereinabove may be useful in reducing flatulence caused by oligosaccharides, these methods have not been successful in substantially removing the flatulence-causing oligosaccharides from the legumes. In addition, these methods have ignored the flatulence caused by other components of the legumes. It has been suggested by researchers, however, that, at least with beans, oligosaccharides account for only about ⅓ of the cause of flatulence, and that ⅔ is caused by other components such as, e.g., undigested starch in the bean. Other research indirectly suggests that the sugars are responsible for the violent xe2x80x9cepisodesxe2x80x9d that occur approximately within five hours after ingestion of the legume, while xe2x80x9cbackground flatulencexe2x80x9d, which occurs regularly over a six to eight hour period after eating, is caused by the non-digested starch. Unfortunately, very little research, in comparison, has been directed to reducing the flatulence caused by these other components.
Recently, Yansoo Chung, in his Ph.D. thesis from Michigan State University (1996), reported that cooking whole navy beans for 10 minutes caused starch crystallization within the cell wall of the navy beans, thus impeding and preventing the digestive enzymes in the stomach from digesting (hydrolyzing) the starch.
Therefore, additional investigations are required to find the appropriate conditions to prevent such crystallization from occurring and thereby enhance the digestibility of these starches in the bean.
In copending application entitled xe2x80x9cA PROCESS FOR REDUCING FLATULENCE IN LEGUMESxe2x80x9d, having U.S. Ser. No. 09/236,314, a process was described which significantly reduced the flatulence of legumes by (1) rehydrating the cleaned legume in a first water bath, (2) soaking and heating the rehydrated legume at a second temperature to permit diffusion of the flatulence-causing oligosaccharides from the legume to the soak water and permit the naturally occurring oligosaccharide reducing enzyme in the legume to digest the remaining flatulence-causing oligosaccharides in the legume, said second temperature being greater than the first temperature but lower than the inactivation temperature of the enzyme; (3) heating the legume to a third temperature under conditions effective to initiate starch gelatinization, said third temperature being greater than the first and second temperatures but less than the temperature to substantially coagulate the protein surrounding the starch in the legume; and optionally blanching the legume. It was indicated in the specification that the order of the steps was important, i.e., after the completion of each step, the temperature was increased to the temperature in the subsequent step and that it was important that oligosaccharide removal was completed before proceeding to step (3) since step (3) was conducted at temperatures above the inactivation temperature of the oligosaccharide reducing enzyme.
However, the present inventors have developed an improved process in which the legumes are soaked at temperatures which are about or greater than the inactivation temperature of the oligosaccharide-reducing enzyme prior to conducting any substantial oligosaccharide reduction in the legume. Moreover, the present inventors have found a process which is substantially more efficient than that which is described in the copending application described hereinabove. Furthermore, the products formed by the present process have consistently less cracking and better texture and mouthfeel.
The present inventors have developed a process which not only produces a legume with reduced flatulence and enhanced starch gelation, but also produces a legume which has the texture, taste, smell, appearance and feelxe2x80x94in short, the organoleptic propertiesxe2x80x94of processed canned or frozen legumes that are commercially sold in the United States.
Thus, the inventors have found an efficient means to effectively reduce the flatulence from the digestion of legumes, such as beans and found a process which produces a low flatulence legume having the organoleptic properties of processed, e.g., canned or frozen legumes, sold commercially.
The present invention is directed to a process for reducing the flatulence caused by the digestion of the legume in mammals, which process comprises:
(1) soaking a legume in a water bath having stagnant, sprayed or flowing water at a first temperature which is above ambient temperature but less than the critical rehydration temperature, under conditions effective and for a period of time sufficient to produce a rehydrated legume having a moisture content which is at least 50% of that of a fully hydrated legume;
(2) heating the product of step (1) in a water bath to a second temperature under conditions effective to increase the moisture content to an amount which is greater than full hydration, said second temperature being greater than the first temperature and the critical rehydration temperature and at or greater than the temperature of inactivation of the oligosaccharide reducing enzyme present in the legume, and less than the temperature of maximum starch gelation;
(3) soaking and heating the rehydrated legume of step (2) at a third temperature which is greater than the critical rehydration temperature but at a temperature less than the second temperature and less than the temperature of inactivation of said enzyme under conditions effective to substantially remove all of the flatulence-causing oligosaccharides therefrom; and
(4) optionally blanching the product of step (4) at blanching effective temperatures, said blanching temperature being greater than the first, second and third temperatures.
In another embodiment of the present invention, the legumes are prepared by the above process with an additional step between steps 1 and 2. More specifically, the product of step (1) is first heated in a soak water bath at a transition temperature which is greater than the first temperature but less than the second temperature.
In still another embodiment of the present process, the soak water is fully or partially drained and replaced with fresh water which is added or bled in during the full or partial drain; this may occur after or even during any of the steps enumerated hereinabove at a rate sufficient to maintain a positive oligosaccharide driving force at a level that minimizes cracking for a time sufficient to reduce the brix of said soak water. This step can be repeated any number of times or executed continuously to reduce the remaining oligosaccharide in the legume to a desired level.
In another embodiment, an aqueous solution of a food grade calcium sequestering agent, such as a phosphate salt, is added to the soak water at a concentration and time sufficient to soften the legumes as desired. The calcium sequestering agent can be added before, during or after any step in the process described hereinabove. However, it is preferably added during or prior to step (1), although it is even more preferable that the legumes are rinsed in a dilute solution thereof during or after step (4), if the legumes are blanched or during or after step (3), if there is no blanching step.
The present invention is also directed to the preparation of a legume exhibiting reduced flatulence when digested by a mammal, which comprises repeating steps (1)-(3) hereinabove, and optionally step (4) and the other steps described hereinabove, and then
(5) mixing the legume product of step (4) with a food acceptable vehicle to form a legume-based mixture; and
(6) treating the product of step (5) under the desired preservation methods.
The present invention is also directed to the product thus formed by the processes described hereinabove.